With the development of science and technology, more and more portable electronic devices such as mobile phones, digital cameras, tablet computers, laptops and the like have become indispensable in people's life. Since the portable electronic devices are generally used by individuals and store some private data, the data stored in the electronic device, such as address books, pictures, personal information and the like, is privately owned. If an electronic device is lost, the data therein may be used by others, which may cause unnecessary losses. An electronic device may be prevented from being used by others by means of password protection. However, a password is easily revealed or cracked. Therefore, the level of data security is low. In addition, users are able to use an electronic device only when they remember the password. If the password is forgotten, much inconvenience may be caused to the users. Therefore, a personal fingerprint identification system has been currently developed for identity authentication to improve data security.
Generally, a fingerprint identification system includes a plurality of pixel modules arranged into an array, wherein each pixel module includes a top-layer electrode and a pixel circuit. As the fingerprint identification system needs to use the top-layer electrode to receive contact of a finger, and is different from typical integrated circuit package, the top-layer electrode needs to be exposed outside the integrated circuit, thereby causing the electrostatic charges to be accumulated in the vicinity of the top-layer electrode. Furthermore, during the manufacturing processes such as wafer sawing and encapsulation etc., the electrostatic charges may also be accumulated in the vicinity of the top-layer electrode. If the electrostatic charges accumulated at the top-layer electrode are too high, the electrostatic charges may generate an electrostatic current, which causes damages to the pixel circuit. On the other hand, the pixel circuit is generally arranged at the top-layer electrode, and the circuit area of the pixel circuit should be less than or equal to the area of the top-layer electrode. In other words, the pixel module (or the pixel circuit) applied in the fingerprint identification system is subject to restrictions of the circuit area, and it is impossible to accommodate an additional electrostatic protection circuit. As a result, the absence of the electrostatic protection function may damage the fingerprint identification system by the electrostatic current. Therefore, how to provide a pixel module and a fingerprint identification system that have an electrostatic protection function becomes an aim in this field.